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LASERS

Efficiency & Strength for Lightweighting

May 11, 2016

Agenda

• Welded Blanks

− Brief history & evolution

− Current & future applications for reducing weight

• Laser Ablation

− Basic principles

− Applications

First Operation Blanking

Laser Welded Blanks (LWB)

Laser welded blanks are manufactured from two or more blanks, of the same or

different steel grades or gauges welded together. A high level of engineering

analysis and laser technology is applied to achieve a reduction in vehicle mass,

number of parts and tooling cost, while improving body strength.

It is important to note, that unlike other welding applications, a welded blank will

be formed after welding. The stresses applied during the forming process

require a very high quality weld placed in the exact location to optimize mass

and material utilization.

Why do we use Welded Blanks?

• Different gauges, materials & coatings can be

incorporated into one blank

− Blank can be engineered to desired properties

• Consolidation of components

− Reduction in number of parts

− Reduced tooling costs

− Reduced assembly operations and equipment

• Material utilization

− Reduction in engineered scrap due to improved blank nesting

• Mass reduction

Shiloh Welded Blank History

• Started welded blank production in 1989

− First welded blank was mash seam welded

− Reclamation of offal from large body blanks

• Moved to laser welding in 1994

− Early systems were 3 kW lamp pumped YAG (4% eff.)

− Current systems are all solid state (45% eff.)

• Current production est. >13,000,000 LWB/yr

• 5 LWB facilities currently

Mash Seam Weld Section & Heat Affected Zones (HAZ)

4.70 mm

0.46

0.9/1.3 mm material welded with Mash Welder, no filler wire

0.31

Laser Weld Section & Heat Affected Zones (HAZ)

0.81 mm

0.2 0.15

0.8/1.6 mm material welded with 4 kW Nd:YAG laser, 600 micron spot, no filler wire

0

20

40

60

80

Thin Base Thin Base

near HAZ

HAZ Thin

Side

Weld Bead HAZ Thick

Side

Thick Base

near HAZ

Thick Base

Har

dnes

s

Advantages of Laser Welding

• Improved speed and flexibility

− Common systems with interchangeable fixtures

• Improved weld quality

− Smaller HAZ

− Reduced work piece distortion

• Improved formability

− Elimination of large step due to overlap welding

− Enhanced capabilities for curvilinear welding

Laser Welding Capabilities

• Linear

• Multi-Linear

• Curvilinear

APPLICATIONS

Current Blank • 15.2 Kg

2 Piece LWB • Total Steel usage = 12.7 Kg

Advantages

• Material savings of

2.5 Kg/part

• Blank A can use

uncoated steel

Applications

Material Optimization – Reduction in engineered scrap

2 Pc. Baseline

Design • Material Usage 5.23 kg

• On Vehicle Mass 2.74 kg

LWB Option • Material Usage 4.38 kg

• On Vehicle Mass 2.38 kg

Reinforcement

1.10 mm

Pillar , 0.90 mm

Blank A, 1.60 mm

Blank B, 0.90 mm

Advantages

• 0.84 kg of Material

savings per side

• 0.36 kg of mass

savings on vehicle per

side (0.72 kg/Veh.)

• Lower stamping die

cost

• No welding or fixture

costs

• Lower press time,

transportation,

inventory

Applications

Part Consolidation

Balance - Formability & Mass Savings B

lan

k

Th

inn

ing

16 % 16 % 33 % 40 %

Vehicle mass optimization example:

For some applications the part geometry requires a high level of material elongation

for forming. Placement of the weld seam is critical. This example shows a solution

to achieve acceptable levels of material thinning by correct placement of the weld

line and mass optimization with curvilinear laser weld.

Applications

Base Design Curvilinear Weld

Option

Blank Gauge in mm

Mass in kg

Thick Blue 1.80 4.75

Thin Green 0.80 4.59

Total 9.34

Blank Gauge in mm

Mass in kg

Thick Pink 1.80 2.75

Thin Brown 0.80 5.48

Total 8.23

-1.11 Kg /Door

Mass Savings

Vehicle Mass Optimization

FUTURE APPLICATIONS

Future Applications

• Advances in laser technology

− Lower cost/kW of laser systems & higher beam quality

− Improved optics and beam delivery

− Short pulse width (laser ablation)

− Removal of coatings prior to welding

− Removal of surface contaminants prior to joining

− Surface structuring

• Laser welding of advanced materials

− AHHS & Gen3 steels

− Thick gauge steels

Future Applications

Thick Gauge Frame Components (3 mm+)

Higher power and lower cost/Kilowatt of the newer solid state

lasers has opened the possibility of bringing welded blank

methodology to thicker gauge truck frame components (3-9 mm

thickness range) to reduce mass and optimize material

utilization.

Initial brainstorming with customers has shown ideas that could

reduce the mass by 25 kg.

Baseline Design Mass = 11.5 Kg

Laser Welded

Option • Mass = 9.6 Kg

Advantage

• 1.9 Kg mass savings

on vehicle

Thick Gauge Laser Welding

Baseline Required blank for stamping

Laser Welding Option

Base blank nesting – not feasible due

to width of the coil (3.0 m or 118”)

Advantages

• Material savings of

25+ kg.

• Several tons of steel

has been taken out of

initial production

which reduces carbon

foot print

• Option to change

material grades and

gages for additional

weight and cost

savings

Thick Gauge Laser Welding

Example – Frame Rail

Rectangular blank

Scrap overlay ~ 25 kg

Blank nesting

PHS & LWB

1. B-Pillar – Hot stamp/AHSS

2. Door Ring – Hot stamp/AHSS

3. A-Pillar – Hot stamp/AHSS

4. Frame rail

5. Side sill

6. Crossmembers

7. Floor pan

8. Cowl side

LASER ABLATION

Pre-Process Surface Preparation

• In many manufacturing applications it is essential to

remove surface contaminants and oxides before further

processing

• Adhesive bonding often requires a “clean” surface so the

adhesive can wet the material creating strong bonds

• Welding components also requires “clean” surfaces to

prevent contaminants from weakening the welds or

causing porosity and leaks

• Some coated PHS must have the coating removed prior to

welding to prevent contaminating the welds

Short Pulse Lasers - Enabling Technology

• Ablation of surface coatings

− Removal of coatings prior to welding

• Ablation of surface contaminants & oxides

− Removal of surface contaminants prior to joining

• Surface structuring

− Texturing to improve or prepare surface for specific

applications

− Creation of super-hydrophobic surfaces

APPLICATION OF SHORT PULSE

LASERS FOR METAL SURFACE

CLEANING

Pulse duration and pulse energy

Two pulses of equal pulse energy but of

different duration

t

Pulse peak power = Pulse energy/time

Oxide Removal

Video courtesy of Trumpf

HOW CLEAN IS CLEAN?

How Clean is Clean?

Everyone will agree that surfaces need to be clean

Not everyone will agree just how clean

the surface needs to be

• Typical cleaning methods include

− Brushing or grinding

− High pressure water blasting

− Attacking with chemicals

• The following developmental work will show:

− A method for estimating Surface energy/cleanliness

using contact angle & Dynes

− Applying a short pulse laser and scanner to clean metals

prior to laser welding or adhesive joining

How Clean is Clean?

• When a drop of liquid is placed on a surface its shape is determined by the

balance of interfacial liquid/solid/vapor forces.

− A high surface tension liquid when placed on a solid of low surface energy will cause

the liquid droplet to form a spherical shape or “bead up”

− Conversely, if the liquid surface tension is lower than the solid surface energy the

droplet has a lower profile and “sheets” or wets the surface.

• By viewing small droplets of liquids the interfacial tension can be observed. The

profile of the droplet can be defined by an angle formed by a line drawn tangent

to the curve of the droplet at the point where the droplet intersects the surface.

The angle formed by this tangent is called the contact angle.

Measuring Material Cleanliness with Dynes

• Contact angle measurement can be used to detect the presence of oxides and contaminants that have a different surface energy than the underlying substrate.

• Fortunate for us, organic contaminants and oxides have much lower surface energies than metals and therefore the contact angle can be taken as a proxy for cleanliness of the surface.

• Surface Tension can be measured in energy units called dynes/cm.

• The most common method of measuring surface energies is by employing ASTM D 7541

Measuring Material Cleanliness with Dynes

EXPERIMENTAL RESULTS

Experimental Procedure

• Empirically determine the laser power density

(fluence) required to achieve the required

cleanliness (dyne) level

• Adjust parameters to optimize cycle times

(Area/sec)

− Avg. laser power

− Spot size/shape

− Pulse repetition rate

− Pulse overlap

− Line overlap

Material Surface Cleaning for Adhesion

Objective

• To provide an efficient surface preparation

process for laminate material joining.

• Material tested:

• Current production coated low carbon steel

• Future non ferrous alloy

Surface Analyst™

Item Name: The Surface Analyst™

Company: Brighton Technologies

Description: Self-contained instrument for

analyzing surface energy

The Surface Analyst™ determines the wetting properties of a surface and

provides a number that correlates to its cleanliness.

Material Surface Analysis Equipment

Approximate Comparisons of

Contact Angle vs Dyne Inks

Surface Condition

Wetting

Tension Range

(dyne/cm)

Contact Angle

Range

(degrees)

Cleanest 72 1-15

50-60 16-32

40-50 33-50

Most

Contaminated 30-40 50-70

Goals & Experimental Set Up

• Goals − Determine if a short pulse laser can obtain required cleanliness

level − Min. 44 dyne

− Determine if cleaning cycle times can meet production requirements − Min. 22.5 cm2/sec

• Experimental set up − Laser

− IPG YLPN-100-25x100-1000-S – max avg. power of 1000 watts − Wavelength 1064 nm − Pulse width 100 ns − Pulse repetition rate 2- 50 kHz

− Scanner − Scanlab intelliSCAN30

− The scanner was mounted on a small gantry system

Surface scanned with an SEM as received.

Contaminants

Surface scanned with an SEM after

20% (200w) ablation power. (Carbon and Oxygen reduced – No Melting)

Surface scanned with an SEM after

30% (300w) ablation power. (Carbon and Oxygen reduced – Melting Begins)

Melting

Galvanized Steel Surface Cleaning

Galvanized Steel Surface Cleaning

Spectrum

Label C O Fe Zn

Cleanliness

(dyne/cm)

As Rec'd 17.85 1.91 0.81 79.43 39

10% 11.81 0.94 0.83 86.42 42

20% 11.05 0.97 0.80 87.18 46

30% 9.55 0.85 0.83 88.76 53

40% 8.52 0.91 0.87 89.69 53

50% 7.56 0.72 0.83 90.90 55

60% 6.30 0.63 0.96 89.25 56

70% 5.98 0.54 0.77 91.70 60

80% 5.70 0.48 1.07 91.75 61

90% 4.85 0.37 0.98 90.69 63

Surface as received 39 Dyne, Target 44 Dyne.

SEM scan - surface cleanliness at different power intervals.

20% (200w) power (Carbon and Oxygen

reduced – No Melting)

30% (300w) power (Carbon and Oxygen

reduced – Melting Begins)

Galvanized Steel Surface Cleaning

Galvanized Low Carbon Steel Summary

• Material received at cleanliness level of 39 dyne/cm − SEM image of the material surface shows visible contaminants

• Surface laser ablation performed; observed that as energy increases,

hydrocarbon contaminations (carbon and oxygen) are reduced − As the fluence increases, the surface becomes cleaner until eventually the surface

begins to melt

• 20% laser power (200 watts) surface cleanliness recorded at 46 dyne/cm − Visual examination of the surface showed a clean surface and no visible

melting points.

• 30% laser power (300 watts) surface cleanliness recorded at 53 dyne/cm − Visual examination of the surface showed again a clean surface but with

some melting points

5182-0 Aluminum Alloy

Surface scanned with an SEM as received.

Contaminants

Aluminum Surface Cleaning

Surface scanned with an SEM after

20% ablation power. (Carbon and Oxygen reduced – No Melting)

Melting

Surface scanned with an SEM after

40% ablation power. (Carbon and Oxygen reduced – Melting Begins)

Surface received 35 Dyne, Target 44 Dyne.

Spectrum

Label C O Mg Al Mn Fe

Cleanliness

(dyne/cm)

As Rec'd 33.86 4.30 3.40 58.04 0.18 0.20 35

10% 16.71 4.01 4.18 74.79 0.19 0.12 41

20% 7.45 3.58 4.48 84.02 0.27 0.19 53

30% 7.59 3.74 4.45 83.82 0.34 0.06 60

40% 8.41 3.59 4.31 85.30 0.24 0.14 63

50% 8.10 3.29 4.15 83.96 0.30 0.21 72

60% 7.57 3.44 4.10 84.34 0.25 0.31 72

70% 8.23 2.93 4.02 84.29 0.28 0.24 72

80% 8.18 2.93 4.00 84.38 0.29 0.23 72

90% 8.04 2.91 3.86 82.15 0.29 0.24 72

Aluminum Surface Cleaning

SEM scan - surface cleanliness at different power intervals.

20% power. (Carbon & Oxygen

reduced – No Melting)

40% power. (Carbon & Oxygen

reduced – Melting Begins)

5182-0 Aluminum Alloy

5182-0 Aluminum Alloy Summary

• Material received at cleanliness level of 35 dyne/cm

— SEM image of the material surface shows visible contaminants

• Surface ablation performed; observed that as energy increases,

hydrocarbon contaminations (carbon and oxygen) were reduced

— As the fluence increases, the surface becomes cleaner until eventually the surface

begins to melt.

• 20% (200 watts) and 30% (300 watts) power surface cleanliness

measured 53 dyne/cm and 60 dyne/cm

— Visual examination of the surface showed a clean surface and no visible melting points.

• 40% (400 watts) power surface cleanliness measured 63 dyne/cm

— Visual examination of the surface showed again a clean surface but with

some melting points.

Aluminum Surface Cleaning

304 Stainless Surface Cleaning

Objective

• To provide an efficient surface preparation process for

stainless steel heat exchanger welding.

• Material tested:

• Current production 304 Stainless steel material.

Goals & Experimental Set Up

Goals • Determine if a short pulse laser can obtain required cleanliness level

− Min. 44 dyne

• Determine if cleaning cycle times can meet production requirements

− Min. 12 cm2/sec

Experimental set up • Laser

− Trumpf TruMicro 7050 disk laser - avg. power of 750 watts, max pulse energy 80 mJ

− Wavelength 1030 nm

− Pulse width 30 ns

− Pulse repetition rate 5-100 kHz

• Scanner

− Scanlab intelliSCAN30

• The scanner was mounted on a small gantry system

Test Material

Target Laser Ablation Results

Clean Rate

(cm2/sec)

Cleanliness

(dyne/cm)

Clean Rate

(cm2/sec)

Cleanliness

(dyne/cm)

Low Carbon Steel 22.5 44

72 46

72 53

5182-0 Aluminum

Alloy 22.5 44

72 53

72 61

304 Stainless

Steel 12 44 30 72

Results Summary

• Data provided supports the proposition that “Short Pulse Laser

Ablation” systems can provide

— Modular and manageable process for many surface cleaning applications

— Desired surface cleanliness

— Expeditious cleaning cycle time

• Future studies to be performed

— Laser ablation cleaning systems with multiple scanner heads sharing energy

form single source laser resonator

— Simultaneous surface cleaning (top & bottom)

— Surface structuring to improve adhesion & lubrication

Conclusions & Future Works

Jim Evangelista jim.evangelista@shiloh.com

Phone: 734-738-1300

Acknowledgments: Short Pulse Laser Development

— Arthur Amidon, IPG

— Bill Shiner, IPG

— Dennis Decker, Trumpf

— Dr. Sascha Weiler, Trumpf

Michael Tymosch mike.tymosch@shiloh.com

Phone: 330-558-2306

Thank You

#GDIS

Presentations will be available May 16

at www.autosteel.org